Then the army under Alva's son, Don Frederick of Toledo, marched northwards, and the sack of Zutphen and the inhuman butchery of Naarden are among the blackest records of history.
It is connected with Amsterdam by a steam tramway, passing by way of the small fortified towns of Naarden and Muiden on the Zuider Zee.
Conde made no headway against Amsterdam, and William retook Naarden (September 14th).
The principal sea-inlets in the north are the Texel Gat or Marsdiep and the Vlie, which lead past the chain of the Frisian Islands into the large inland sea or gulf called the Zuider Zee, and the Wadden or " shallows," which extend along the shores of Friesland and Groningen as far as the Dollart and the mouth of the Ems. The inland sea-board thus formed consists of low coasts of sea-clay protected by dikes, and of some high diluvial strata which rise far enough above the level of the sea to make dikes unnecessary, as in the case of the Gooi hills between Naarden and the Eem, the Veluwe hills between Nykerk and Elburg, and the steep cliffs of the Gaasterland between Oude Mirdum and Stavoren.